Laboratory Simulation of Flow through Rough-Walled Microfractures under High Hydraulic Gradient

Laboratory experiments on fluid flow through fracture are important in solving the fluid-in-rush problems that happen during the tunnel excavation. In order to study the mechanism of fluid flow through a rough-walled microfracture, fluid flow experiments were carried out and the fiber Bragg grating (FBG) strain sensors were applied to monitor the deformation of the microfracture surface during the seepage process. Considering the difficulty of collection of undisturbed rock samples from the deep locations, a methodology to simulate fluid flow through a fractured rock mass using analog materials containing a single fracture was developed. This method is easy to simulate the fluid flow through a fracture of certain aperture. Experimental data showed that Forchheimer equation could provide an excellent description of the nonlinear relationship between hydraulic gradient and flow velocity, and the variations of Forchheimer coefficients with joint roughness coefficient (JRC) were studied. It was found that the deformation of the microfracture surface subjected to seepage could be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrated that the surface strain is significantly affected by hydraulic pressure.

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A Unified Equation to Predict the Permeability of Rough Fractures via Lattice Boltzmann Simulation

Water ◽

10.3390/w11051081 ◽

2019 ◽

Vol 11 (5) ◽

pp. 1081 ◽

Cited By ~ 4

Author(s):

Peijie Yin ◽

Can Zhao ◽

Jianjun Ma ◽

Linchong Huang

Keyword(s):

Numerical Simulation ◽

Fluid Flow ◽

Lattice Boltzmann ◽

Mass Conservation ◽

Extensive Study ◽

Roughness Coefficient ◽

Single Fracture ◽

Lattice Boltzmann Simulation ◽

Wide Range ◽

Flow Through

In this paper, the fluid flow through rough fractures was investigated via numerical simulation based on the lattice Boltzmann method (LBM). The accuracy of LBM was validated through the numerical simulation of the parallel plate model and the verification of the mass conservation of fluid flow through rough fracture. After that, the effect of roughness on fluid flow was numerically conducted, in which, the geometry of fractures was characterized by the joint roughness coefficient (JRC), fractal dimension (D) and standard deviation (σ). It was found that the JRC cannot reflect the realistic influence of roughness on the permeability of single fracture, in which, an increase in permeability with increasing JRC has been observed at the range of 8~12 and 14~16. The reason behind this was revealed through the calculation of the root mean square of the first derivative of profile (Z2), and an equation has been proposed to estimate the permeability based on the aperture and Z2 of the fracture. The numerical simulations were further conducted on fluid flow though synthetic fractures with a wide range of D and σ. In order to unify the parameter that characterizes the roughness, Z2 was obtained for each synthetic fracture, and the corresponding relationship between permeability, aperture and Z2 was analyzed. Meanwhile, it was found that the fluid flow behaves differently with different ranges of Z2 and the critical point was found to be Z2 = 0.5. Based on extensive study, it was concluded that Z2 is a generic parameter characterizing the roughness, and the proposed equation could be used to predict the permeability for fluid flow in fracture.

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Estimation of Tortuosity of Fluid Flow Through a Single Fracture

Journal of Canadian Petroleum Technology ◽

10.2118/03-12-03 ◽

2003 ◽

Vol 42 (12) ◽

Cited By ~ 18

Author(s):

S. Murata ◽

T. Saito

Keyword(s):

Fluid Flow ◽

Single Fracture ◽

Flow Through

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A novel three-dimensional discrete fracture network model for investigating the role of aperture heterogeneity on fluid flow through fractured rock masses

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2019.03.014 ◽

2019 ◽

Vol 116 ◽

pp. 25-37 ◽

Cited By ~ 8

Author(s):

Na Huang ◽

Yujing Jiang ◽

Richeng Liu ◽

Bo Li ◽

Satoshi Sugimoto

Keyword(s):

Fluid Flow ◽

Network Model ◽

Fractured Rock ◽

Three Dimensional ◽

Fracture Network ◽

Discrete Fracture Network ◽

Discrete Fracture ◽

Flow Through ◽

Fractured Rock Masses

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95/04880 Heat extraction modelling from forced fluid flow through simulated fractured rock masses: Application to the Rosemanowes hot dry rock reservoi

Fuel and Energy Abstracts ◽

10.1016/0140-6701(95)96640-x ◽

1995 ◽

Vol 36 (5) ◽

pp. 347

Keyword(s):

Fluid Flow ◽

Fractured Rock ◽

Heat Extraction ◽

Rock Masses ◽

Hot Dry Rock ◽

Flow Through ◽

Fractured Rock Masses

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Experimental Study on Stress-Dependent Nonlinear Flow Behavior and Normalized Transmissivity of Real Rock Fracture Networks

Geofluids ◽

10.1155/2018/8217921 ◽

2018 ◽

Vol 2018 ◽

pp. 1-16 ◽

Cited By ~ 6

Author(s):

Qian Yin ◽

Hongwen Jing ◽

Richeng Liu ◽

Guowei Ma ◽

Liyuan Yu ◽

...

Keyword(s):

Fluid Flow ◽

Rock Fracture ◽

Hydraulic Gradient ◽

Nonlinear Flow ◽

Fracture Networks ◽

Critical Hydraulic Gradient ◽

Boundary Load ◽

Flow Through ◽

Stress Dependent ◽

Rock Fracture Networks

The mechanism and quantitative descriptions of nonlinear fluid flow through rock fractures are difficult issues of high concern in underground engineering fields. In order to study the effects of fracture geometry and loading conditions on nonlinear flow properties and normalized transmissivity through fracture networks, stress-dependent fluid flow tests were conducted on real rock fracture networks with different number of intersections (1, 4, 7, and 12) and subjected to various applied boundary loads (7, 14, 21, 28, and 35 kN). For all cases, the inlet hydraulic pressures ranged from 0 to 0.6 MPa. The test results show that Forchheimer’s law provides an excellent description of the nonlinear fluid flow in fracture networks. The linear coefficient a and nonlinear coefficient b in Forchheimer’s law J=aQ+bQ2 generally decrease with the number of intersections but increase with the boundary load. The relationships between a and b can be well fitted with a power function. A nonlinear effect factor E=bQ2/(aQ+bQ2) was used to quantitatively characterize the nonlinear behaviors of fluid flow through fracture networks. By defining a critical value of E = 10%, the critical hydraulic gradient was calculated. The critical hydraulic gradient decreases with the number of intersections due to richer flowing paths but increases with the boundary load due to fracture closure. The transmissivity of fracture networks decreases with the hydraulic gradient, and the variation process can be estimated using an exponential function. A mathematical expression T/T0=1-exp⁡(-αJ-0.45) for decreased normalized transmissivity T/T0 against the hydraulic gradient J was established. When the hydraulic gradient is small, T/T0 holds a constant value of 1.0. With increasing hydraulic gradient, the reduction rate of T/T0 first increases and then decreases. The equivalent permeability of fracture networks decreases with the applied boundary load, and permeability changes at low load levels are more sensitive.

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Research Advance in Fluid Flow through a Single Rock Fracture

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.204-208.628 ◽

2012 ◽

Vol 204-208 ◽

pp. 628-634

Author(s):

Bao Hua Guo ◽

Cai Xia Tian

Keyword(s):

Fluid Flow ◽

Fractured Rock ◽

Rock Fracture ◽

Research Work ◽

Engineering Practice ◽

Flow Through ◽

Research Advance ◽

Single Rock Fracture ◽

Fractured Rock Masses ◽

Channeling Flow

Flow properties through a single rock fracture are the foundation of researching fluid flow in fractured rock masses. Many researchers at home and abroad are engaging in this subject for the urgent need of engineering practice. This article mainly introduces concepts of roughness, aperture, tortuosity, channeling flow, and influencing factors of stress, temperature, anisotropic, inlet head, scale effect, solution etc. Finally, some research work should be done in future are given.

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